By signing up, you agree to the Code of Conduct, which applies to all online and in-person spaces managed by the Public Lab community and non-profit. You also agree to our Privacy Policy.

As an open source community, we believe in open licensing of content so that other members of the community can leverage your work legally -- with attribution, of course. By joining the Public Lab site, you agree to release the content you post here under a Creative Commons Attribution Sharealike license, and the hardware designs you post under the CERN Open Hardware License 1.1 (full text). This has the added benefit that others must share their improvements in turn with you.

Soil Testing at the Houston Barnraising

Sunday at the
Barnraising we went to Tidwell Park in Houston. The park is right by the
community center and has active baseball and soccer fields, basketball courts,
a playground, and a nature trail that runs alongside Halls Bayou. We spent some
time balloon mapping, then a group went to do some soil testing along the banks
of the bayou.

The community around
the park is concerned about contaminants in the soil, because the bayou
at the back of the park flooded during Hurricane Harvey, and backs up regularly.
Hurricane
Harvey re-distribute(d) contaminants from nearby oil and gas industry sites,
Superfund sites, and wastewater treatment plants throughout Houston and left
contaminants- such as heavy metals and polycyclic aromatic hydrocarbons (PAH's)-
behind on the soil as it drained. These contaminants are absorbed by the soil
and can stay on the top of the soil where people can be exposed to them, or
move through the soil profile to the groundwater. This poses a public health
issue, as exposure to these contaminants- especially for children- can have
negative health effects. One study done with soil samples pre and post Harvey
in Manchester neighborhood, Houston, found that PAH's were widespread throughout
the neighborhood, and that they were moved around during Harvey. Read more at: https://phys.org/news/2018-02-texas-pollution-hurricane-harvey.html#jCp

**What did
we test for? **

We tested the soil for heavy metals, PAH's, and PCB's given the
community's concerns, the site history, and the risk of exposure for children playing
at the park and people living nearby and/or fishing in the bayou. This type of
soil testing can contribute to 'baseline data' in environmental justice
neighborhoods and help the understanding of what contaminants have been left
behind in the soil and water as a result of the industry in Houston and the
flooding events associated with the hurricane so that people have information
to reduce exposure to these contaminants of concern and be informed about the
impacts of industry in their area.

*Gathered around the soil testing kits- the Hanby Field Kit for testing for Petroleum Hydrocarbons and soil sampling kit from Citizen Science Community Resources.

Heavy metals (like Arsenic, Barium, Lead, Cadmium, Zinc
and Mercury) do not break down, and can move around in floods and build up in
soils. They are toxic at certain concentrations, and Arsenic and Mercury are
particularly concerning in this context because they can be transformed in
water and through the activity of microorganisms into more toxic and
bioavailable forms.

Polycyclic aromatic hydrocarbons (PAH's)
are known to be carcinogenic (cancer causing) and are associated with the
burning of fossil fuels, so are likely in this context given the proximity to oil
and gas industry and previous studies confirming their presence.

Polychlorinated biphenols (PCBs) are another
contaminant of concern, because exposure to them can lead to neurobehavioral and
immunological changes in children; and they are known to cause cancer in
animals. They are known to build up in fats, especially in fish and seafood, and
because we know that people fish in the bayou, we wanted to test for these too.

We took soil samples from the top 1-3 inches of soil at
various locations along the bayou. We took them from the top layer of the soil
because that is where we would expect contaminants to settle after flooding,
and also where people are most likely to be exposed to these contaminants. We
used Citizen Science Community Resources awesome "Soil Sampling Kit" to take
the samples **_(pictured below: ******____**__********"mso-bidi-font-weight:normal">"mso-bidi-font-weight:normal">="mso-bidi-font-style:normal">Evan
James is in Galveston TX at #txbarnraising
with Public
Lab showing off Citizen Science Community Resources DIY soil sampling
toolkit to help communities impacted by #climatechange)._**

_
_

People taking samples wore gloves (to stay safe and limit
exposure to possible contaminants) and used a trowel that we cleaned with isopropyl
alcohol to take samples. We took 6 samples to send to Test America, a
professional lab, for analysis for heavy metals, PAH's, and PCB's. The lab
provides sample collection containers, labels, and a cooler to keep the samples
in until they are delivered to the lab. Soil samples being tested for heavy metals
do not need to be kept on ice or refridgerated because quantity does not change,
but any 'organic contaminant' such as PAHs and PCB's do need to be kept in
dark, sealed, glass containers and kept cool until analysis by a lab because
they can change in different temperatures and with exposure to air, thus
altering (reducing, typically) the accuracy of your test results.

We also practiced some of the soil analysis methods we
learned earlier in the Barnraising, in a session on soil testing. We used the
Hanby Field Kit for Petroleum Hydrocarbons to test for PAH's, PCB's and a range
of petroleum products. You can read more about the process and methods for
using the Hanby kit here.

Kits like the Hanby use a process where you get the soil
contaminants into solution by shaking them up with a solvent. Then you add a reagent,
a chemical which reacts with the contaminant and produces a certain reaction, a
color change. You then compare the color in the tube with a chart with the known
colors produced by certain contaminants.

This method is more affordable than testing through a
professional lab- the kit costs $1295 to purchase, and comes with 15 tests.
Each test after that costs $15/test, as compared to $90-300 per sample through a
lab. It is fairly simple to use and is an EPA-approved method, meaning it provides
results that would hold up in court and be considered good science. ****

This project was made possible with support from the National Geographic Society.

2 Comments

The Hanby test kit and others (yes, there are other portable units) should only be used for screening purposes, per EPA. Nothing can be comparable to results from a certified lab. Hanby method also has some other limitations: per epa document https://clu-in.org/characterization/technologies/color.cfm
"The limitations of the Hanby Field Test Kit may include inaccurate comparison of color if the sample is dark in color. Further, concentrations may be underestimated for highly refined petroleum fuels (those that are lacking in aromatic compounds). Interpretation of results may be inaccurate because of interference from other petroleum fractions."